In communication networks, such as telephone networks and data networks including the Internet, information may be sent along a path from a source device to a destination device. The source device and the destination device may be, for example personal computers, servers such as email servers, web servers, or file servers, or other electronic devices capable of sending and/or receiving information via the network.
The information may pass through one or more forwarding devices, such as routers or other electronic devices having the ability to forward the information to another device. The intermediate devices may receive the information and use functions, algorithms, data structures, and rules to determine where and how to forward the information so that the information moves towards its intended destination. These functions, algorithms, data structures, and rules form the “forwarding plane” of the network. The functions, algorithms, data structures, and rules of the forwarding plane may be implemented and/or enforced by one or more forwarding devices in the network.
For example, a forwarding device may receive a packet on an inbound interface, look up the destination address of the packet, and apply a rule which causes the forwarding device to look up the destination address in a particular routing table. The routing table may provide a list of “next destinations” which represent a device to which the packet should be sent. The next destination for a particular packet might be, for example, the final destination device or another intermediate forwarding device. The next destination may be identified by an address stored in the routing table. The next destinations stored in the routing table may be indexed by a final destination of the packet. Thus, by looking up the final destination of the packet (e.g., as identified by a header of the packet), one can retrieve the next destination from the routing table. The forwarding device may then forward the packet on an outbound interface to the identified next destination.
Certain aspects of the forwarding plane can affect the efficiency of the network. These aspects include the specific rules, algorithms, data structures, and functions employed, the manner in which the forwarding plane is implemented, and the location at which the forwarding plane is implemented and/or enforced.